CT chest abdomen pelvis doses in Scotland: has the DRL had its day?

Abstract

Objective: This article reports on a pilot study designed to collect dose data representative of current CT chest abdomen pelvis (CAP) practice in Scotland, make any immediately obvious interventions and to identify if the current UK diagnostic reference level (DRL) of 940 mGy cm is still appropriate. The aims are to identify if a Scotland-wide picture archiving and communication system (PACS)-based dose audit of a number of CT examinations is likely to have value in terms of optimization of patient doses and to comment on the significance of the results in terms of future optimization strategies. Methods: Dose audit of CT CAP examinations at 32 different scanner sites across Scotland using accepted data collection and analysis methods. The minimum sample size was 30. Results: Results indicate that CT CAP doses are lower than those previously reported (median, 800 mGy cm, 75th percentile 840 mGy cm) but follow a distribution that is not in keeping with the concept of DRLs as presently understood or implemented. Conclusion: There is value in a PACS-based dose audit project to provide serial snapshots of patient doses as optimization efforts take place and to revise current knowledge about CT doses. In our opinion, the results call into question whether DRLs or the concept of "achievable dose" are suitable for devising optimization strategies once a certain degree of optimization has taken place. Advances in knowledge:The results reported here suggest that it may be time to take a different approach to optimization, concentrating on tools that are more refined than the DRL, which may have become more of a compliance tool than an aid to optimization.

Radiation dose from multidetector CT studies in children: results from the first Italian nationwide survey

“…Furthermore, the dose required to get a specific image quality strongly depends on the equipment used. The DRL term itself can be confusing because complying with a diagnostic "reference" dose is not necessarily the same as following the ALARA (as low as reasonably achievable) principle in that there is no scope for further reduction of radiation exposure [26]. The implementation of robust quality indices could be a further step toward dose optimisation.…”

ICRP Publication 135: Diagnostic Reference Levels in Medical Imaging

“…(2012) with permission from Public Health England]. LAT, lateral; AP, antero-posterior; PA, postero-anterior. (116) Findings from a recent survey of CT doses for hospitals throughout Scotland have revealed a different pattern from the log-normal distributions of DRL quantities seen previously, and may demonstrate a new trend (Sutton et al., 2014). The number of CT scanners is more limited than other types of x-ray equipment, and in the UK, there are more diagnostic radiology physicists engaged in optimisation of CT examinations.…”

Automatic calculation of patient size metrics in computed tomography: What level of computational accuracy do we need?

“…Computed tomography (CT) is a powerful diagnostic tool, but CT imaging protocols should be optimized to minimize radiation exposure. Diagnostic reference levels (DRLs) have been a powerful tool in dose optimization, by establishing typical values of volume CT Dose Index (CTDI vol ) or dose‐length product (DLP), for certain types of examinations performed on standard‐sized (70 ± 3 kg) patients …”